Corrosion protection of metals



Patented Nov. 26, 1946 UNITED AATES OFWE CORROSION PROTECTION OF METALS Willis G. Routson, Berkeley, Calif., asslgnor to Shell Development Company, San Francisco, Calif., a corporation of Delaware No Drawing. Application August 11, 1943, Serial No. 498,4

11 Claims.

The present invention relates to metals or metal-containing articles of manufacture which are normall subject to corrosion and which have been rendered substantially non-corrodible by treatment with a dispersion of certain nitrogen containing organic compounds in a. suitable vehicle. It alsorelates to compositions having anticorrosive, and especially rust-protective properties, and more particularly deals with compositions comprising a substantially neutral vehicle such as normally liquid or normally solid hydrocarb'ons (e. g., fatty oils and natural Waxes) alcohols, ethers, water, etc., containing finely dispersed small amounts of such an organic nitrogen compound.

Metallic surfaces, particularly those contain- 2 phere so that its rusting is prevented or at least retarded. Still another purpose is to protect mechanical equipment from rusting, which equipment stands idle and/or is shipped over long distances. A further object is to provide slushing oils of improved rust-protective properties particularly adapted to withstand the effects of maing iron, require protection against the hazard of a corrosion in the presence of water. To illustrate:

Moisture readily attacks finished or semi-finished metal objects unless the metal surface is covered during storage or shipment by a protective coating such as is imparted by a slushing oil; water the'rate of deterioration of various organic compounds with which they come in contact or they may enter between moving parts of machinery where they act as abrasives.

It is a purpose of this invention to treat metals or articles of manufacture containing metals in a way so that they become resistant to normal corrosion. It is a specific purpose to treat in a simple manner accurately machined metal parts so that they may be handled without developing corrosion, particularly in places where fingerprints have been left. Another purpose is to protect iron or steel equipment exposed to the atmosthe latter is considered as included with the rlne environment. Another purpose is to produce lubricating compositions suitable for "internal combustion engines which compositions. possess improved anti-corrosive, anti-wear, and/or, other 7 Still other objects, will be:

beneficial properties. apparent from the present description."

This invention is based on the discovery that certain organic nitrogen compounds (as hereafter described) have valuable and unexpected rust protective and otherbeneficial properties. These compounds having, say, upward of about '10 carbon atoms and more preferably '12 or more carbon atoms, which are substantially oil-soluble,

may advantageously be employed in ailubri'cat-- ing composition or other oily medium. llowever, the compounds of the invention may be dispersed in either oily or non-oily media although not with the same efiectiveness. v l

The nitrogen compounds of the present invention are characterized by the presence of a nitrile (CN) nitro (NOa) or nitroso (NO) group. (Since may be found in equilibrium with the isomeric form Y nitroso compounds.) These nitrogen-containing radicals are attached to a carbon atom which is not -more than three atoms removed from an acidic group. 'The acidic radical may be COOH, CSOH, GOSH, 'CSSH, SOsH, POsH, and the like. Preferably this acidic radical is attached to a carbon atom which is alpha or beta to the carbon atom carrying the nltrile, nitro or nitroso group, p.

since the rust retarding properties are greater the nearer together these two radicals are. The carboxylic acid radical and the nitrile radical are the preferred radicals of their respective groups.

The present compounds may thus be represented by the formula:

in which X is a radical containing an acidic hydrogen atom, R and R" (which may be the same or different) are hydrogen atoms or hydrocarbon or substituted hydrocarbon radicals, Y is a nitrile, nitro or nitroso radical, R is a hydrocarbon or substituted hydrocarbon radical and n is 0, 1, 2 or '3, but preferably or 1. Preferable values. for R and R" are hydrogen and/or low molecular weight aliphatic radicals such as methyl, ethyl, propyl, butyl, 'etc. R may also contain an ether type linkage which contains an oxygen, sulfur, selenium or tellurium atom. A preferred group of these latter compounds are those in which this ether linkage is attached to the nitrile, nitro, or nitroso containing carbon atom as represented by the formula in which Z is 0, S, Se, or Te.

The several hydrocarbon radicals of the for- Piperidine RzCO+HzC--C OOEt Na r etc., and should preferably be free from highly bonyl, amino, hydrosulfide, etc. For maximum stability against deterioration by oxidation, the acid should not contain more than one olefinic double bond per hydrocarbon radical, and more preferably none. Examples of such hydrocarbon radicals are methyl, ethyl, propyl, isopropyl, normal butyl, isobutyl, secondary butyl, tertiary butyl, normal pentyl, isopentyl, secondary pentyl, hexyl, normal octyl, iso-octyl, normal decyl, isodecyl, dodecyl, tetradecyl, cetyl, stearyl, trimethyl octodecyl, allyl, methallyl, crotyl, methyl vinyl carbinyl, butenyl, pentenyl, hexenyl, propargyl, geranyl, oleyl, phenyl, naphthyl, anthryl, tolyl, xylyl, secondary butyl-naphthyl, dipropylnaphthyl, benzyl, naphthyl-butyl, phenethyl, vinyl-phenyl, crotonyl-naphthyl, methallylphenyl, naphthyl-allyl, 2-phenyl-ethenyl, phenyl vinyl carbinyl, cinnamyl, acetyl, propionyl, caproyl, stearacyl, benzoyl, ethyl-cyclohexyl, tributyl-cyclohexyl, cyclopentenyl, cyclohexenyl, vinyl cyclohexenyl, thioneyl, pyrrolyl, pyridyl, furyl, butyl carbothionyl, octyl carbothionyl, decyl carbothionyl, etc.

A preferred group of oil-soluble compounds are those in which the organic radical or radicals have a total of not less than about 8 carbon atoms and more preferably at least 10 or 12 and up to about carbon atoms for good anti-corrosive properties.

These compounds may be produced, for example, by reactions such as the following:

H2O H polar substituents,such as hydroxyl,carboxyl,cartained by caustic alkali extraction of relatively high-boiling straight-run petroleum oils. such as kerosene, gas oil, lubricating'oils, etc., may also be used, as well as synthetic naphthenic acids, such as cyclohexyl acetic, cyclohexyl propionic, cyclohexyl stearic acids, corresponding alkyl cyclohexyl, tetrallyl, dicyclohexyl fatty acids, or acids derived from naphthenes obtained by hydrogenation of isophorone, diisophorone and homologues, etc.

Another group of carboxylic acids comprises the group of hydroxy acids such as hydroxy benzoic', hydroxy naphthenic, etc., acids and the alkyl homologues thereof, typical representatives being the alkyl salicylic acids.

The dispersion of the present anti-rusting compounds may be a true or colloidal solution in a suitable vehicle which is capable of flowing under the conditions of use, i. e., is liquid or plastic at the temperature employed. Both true solutions and colloidal dispersion in various vehicles are effective in the matter of corrosion protection. However, true solutions are preferred for two reasons: first, colloidal solutions may, under many circumstances, coagulate, in which case the active protectiv agent would be eliminated; and second, colloids tend tocause emulsification of oily vehicles with water, emulsification in many instances being very undesirable as in the lubrication of steam turbines.

The treating temperature for metals is preferably about room temperature if the vehicle is normally liquid, although lower or higher temperatures may be employed. The lower temperature limit is usually determined by the solidification temperature of the liquid, and temperatures should be below the boiling temperature of the vehicle and below the decomposition temperatures of-both the vehicle and'the nitrogen compound.

, Metals capable of being thus protected are in particular the ferrous metals, e. g., softiron,

various steels, cast iron, and to a lesser extent copper, brass, bronze, zinc, aluminum, magne-.

sium' alloys, various bearing metals as copperlead,cadmium-nicke1, silver-nickel, etc.

Articles containing these metals are too nu-' merous to recite. However, it may be mentioned that the problem of rust prevention is critical,

for-example, where accurately machined parts are involved such as piston rings, engin'e'cylinders, bearing shafts, plungers of pumps, etc. In

ings which are piled-up and often set in the openfor months before-being finished.

sprayed with a suitable dispersion, and then stored away. On the other hand, if rust prevention in a steam turbine is desired, it is preferable that the circulating lubricating oil contain the active rust-preventive compound and contact is made as long as this oil is used. Should, after a while, this oil be discarded and be replaced by another one not containing a rust-preventive. then corrosion protection usually lasts for a long time thereafter, due to the protective film left behind. In cases where this film is mechanically destroyed, as in bearings or gears, etc., running under extreme loads, the protective film must be renewed continuously, otherwise rust protection fails.

, The vehicles to which the compounds of this invention may be added for the purpose of producing corrosion-protective compositions may be divided into several groups. In the first place, they may be liquids or plastics, the only requirements as to their physical stat being (in addition to their being able to act as carrier for the acids under normal atmospheric conditions) that they be spreadable over metal surfaces. Spreading may be accomplished by immersing, flooding; spraying, brushing, trowelling, etc. After being applied, all or part of the vehicle may evaporate, or it may be more or less permanent. In other words, both volatile carriers may be used, or substances which do not materially volatilize under normal atmospheric conditions. As to chemical requirements, the vehicle must be stable under ordinary conditions of storage and use and be inert to the active inhibitors.

Thus the vehicle should preferably besubstan tially neutral, although it may be weakly acidic or basic, preferably having a dissociation con-'- instances this may be beneficial.

- Both polar and non-polar vehicles may b employed. Among the former are water; alcohols, such as methyl, ethyl, propyl, isopropyl, butyl,

amyl, 'hexyl, cyc lohexyl, heptyl, methyl cycloa hexyl, octyl, decyl, lauryl, myristyl, cetyl, stearyl, benzyl, '-etc., alcohols; polyhydric alcohols ,as

ethylene glycol, propylene glycol, butylene glycol,

I glycerol, methyl glycerol, etc.; phenol and various Corrosion may be due not only to atmospheric exposure, but; may be caused or accelerated by contact with acidic materials, for example,- by

touching with the fingers. It may also occur in closedsystems, as in internal combustion engines, steam turbines, pipe lines, etc., due to the corrosive influence of various impurities such as water,

oxygen, carbon dioxide, salts, inorganic or organic acids, etc.

The treatment, according to this invention, for the prevention of corrosion may consist of a single contact of the metal to be protected with the dispersion or piece of equipment or both. The choice usually dictated by circumstances. Forexample,

V V of any particular'type of these treatments is alkyl phenols; ketones as acetone, methyl ethyl ketone, diethyl ketone, methyl propyhmethyl' butyl, dl'propyl ketones, cyclohexanone and higher ketones; keto alcohols as benzoin; ethers'as diethyl ether, diisopropyl ether, diethylene diox ide, beta-beta dichlor diethyl ether, diphenyl methyl ether, corresponding ethyl, propyl, bu'tyl ethers; neutral esters of carboxylic and other 65.

acids as ethyl, propyl, butyl, amyl, phenyl, cresyl and higher acetates, propionates, butyrates; lac'-. tates, laurates, myristates, palmitates, stearates,

oleates, ricinoleates, phthalates, phosphates,

phosphites, thiophosphates, carbonates; natural waxes as carnauba. wax, candelillia wax, Japan wax, jojoba oil, sperm oil; fats as tallow, lard oil,

quinolines, pe--.

7 Vehicles of little or no polarity comprise hydrocarbons or halogenated hydrocarbons as liquid butanes, pentanes, hexanes, heptanes, octanes,

benzene, toluene, xylenes, cumene, tetraline, in-

dene, hydrindene, alkyl naphthalenes; gasoline distillates, kerosene, gas oil, lubricating oils (which may be soap-thickened to form greases), petrolatum, paraflin wax, albino asphalt, carbon tetrachloride, ethylene dichloride, propyl chloride, butyl chloride, chlor-benzol, chlorinated kerosene, chlorinated paraffin wax, etc.

The amounts of the present compounds which must be incorporated in the above vehicles to produce corrosion-protective compositions vary considerably with the type of vehicle used. As a general rule, the presence of resinous materials, particularly those of a, colloidal nature, calls for relatively larger amounts of inhibitors. Resinous materials which interfere with the activity of the inhibitors comprise asphaltenes, petroleum resins, various other natural resins, as rosin, resins formed by polymerization of drying fatty oils, phenol-formaldehyde resins, glyptal type resins formed by esterificatlon of polyhydric alcohols with polycarboxylic acids, etc.

In the absence of such resinous materials, amounts required of the nitrogen compounds vary from about 0.001% up to about 0.1%, although larger amounts may be .used. However, where the rust retarding compounds are in colloidal dispersion, rather than in true solution, a concentration in excess of about 0.1% may result in relatively quick loss of part of the inhibitor by precipitation and settling.

In the presence of'resins and other colloids, amounts in excess of 0.1% and up to say may be required. Inasmuch as resins may act as protective colloids, compositions containing these larger amounts of colloidally dispersed inhibitors, together with resin, may be quite resistant to precipitation and settling.

Since resinous and gummy substances in the vehicles do call for greater amounts of inhibitors, it is usually desirable to refine normally liquid vehicles thoroughly and free them from gummy substances, thereby imparting to them maximum inhibitor susceptibility. This is of particular importance, for example, in lubricating oils, specifically steam turbine oils, which are advantageously highly refined before the inhibitor is introduced. Suitable refining treatments include, for example, extraction with selective solvents for aromatic hydrocarbons such as liquid sulfur dioxide, phenol, furfural, nitrobenzene, aniline, beta-beta-dichloro-diethyl ether, antimony trichloride, etc.; treatment with AlCla, sulfuric acid, clay, etc. If the treatments produce a sludge, special care must be taken to remove it very thoroughly and completely.

It has also been found advantageous to incorporate together with the nitrogen compound in an appropriate medium, particularly in a lubricating oil or other nongaseous hydrocarbon (e. g., gasoline, Diesel fuel, kerosene, gas oil, petroleum, plastics, petrolatum, etc.) small amounts of certain oil-soluble dicarboxylic acids or hydroxy aromatic carboxylic acids possessing corrosion protective properties. Acids possessing this property are those having at least 12, and preferably 20 or more carbon atoms, and it is desirable that their active radicals, i. e., the several carboxylic radicals, or carboxylic and hydroxyl radicals, as the case may be, be as close to each other as possible and be separated from each other by not more than 4, and preferably by not more than 2,

intervening atoms. Stability of the acids under conditions to which the compositions are exposed is an added requirement.

Among the dicarboxylic acids which are particularly useful for preventing corrosion are various alkylated aliphatic dicarboxylic acids such as alkylated succinic, glutaric, adipic, etc. acids. If

desired, these acids may contain various substitution radicals as hydroxyl, ether, amino, nitro, hydrosulfide, sulfide, halide, etc., radicals, the most important limiting factor being the necessary stability. In general, it is preferred to use a saturated aliphatic dicarboxylic acid having the carboxyl radicals as close to each other as possible as is consistent with the requirement for stability. Particularly effective are alkyl succinic acids having at least 16, and preferably 20 to 40 carbon atoms.

Of the hydroxy carboxylic acids, hydroxy aromatic carboxylic acids in which the hydroxy radical is directly attached to the aromatic nucleus are most useful; for example, various alkyl phenol or naphthol carboxylic acids wherein the carboxylic acid radical is attached to the nucleus directly or through a carbon linkage, e. g., alkyl salicylic acids, preferably those whose alkyl radicals contain 12 or more carbon atoms.

The addition of these auxiliary acids to hydrocarbon oils containing the primary anti-corrosives is of greatest importance when dealing with wellrefined hydrocarbon compositions. Conventional refining methods, such as acid and alkali treatment, solvent extraction, hydrogenation, etc., remove naphthenic and other monocarboxylic acids which may naturally be contained in the hydrocarbons in small amounts and which may enhance the action of the anti-corrosives. However, even if small amounts of naphthenic and similar acids are naturally present, in general the addition of further amounts of the auxiliary acids of the type described is beneficial. Without wishing to be committed to a particular theory of why this combination of nitrogen compound and dicarboxylic acid produces such an effective antirusting combination, it seems that the nitrogen compound more rapidly forms a protective film than the dicarboxylic acid so that the nitrogen containing compound yields better initial (or quicker) protection while the dicarboxylic acid produces enhanced ultimate protection.

The nitrogen compound, in addition to affording rust protection itself, also promotes the formationof a protective film of the dicarboxylic acid on a metallic surface. This combination of nitrogen compound and dicarboxylic acid is particularly important in connection with the rust inhibiting of highly refined lubricating compositions such as turbine oil since the-refining treatment may render the nitrogen compound only sparingly soluble in the finished oil. Thus a refined Mid-Continent 400 vis. at F. turbine raifinate may only dissolve about 0.015% of alpha stearic acid while it will dissolve about 5% alkyl succinic acid obtained by condensation of maleic anhydride with higher molecular weight olefins (Ex C12-C3o) and subsequent hydrolysis to the acid.

In general, amounts of these auxiliary dicarboxylic acids between about 0.001% and 0.1% may be used in petroleum distillate oils; in bright stocks up to about 1% is indicated, while in plastic compositions higher amounts, even up to 5-10%, may be useful.

The invention may be further illustrated by reference to the following modified Kuebler or Westinghouse corrosion tests. Steel strips (3"x "x were completely immersed in 460 ml. samples of oil which were continuously agitated with electric motor-driven glass stirrers. Thirty minutes after starting, 10% volume of synthetic sea water was added to each sample.

- The tests were continued for 48 hours at a controlled temperature of 75 C. and the amount of rusting on the strips .then noted. (The synthetic sea water was made up from the following formula: in 1000 ml. water-11.0 g. MgClz'GHsO; 4.0 g. NazSO4 (anhydrous); 1.2 g. CaClz (anhydrous); 25.0 g. NaCl.)

Results were as follows:

, l0 phenol, pentamethyl phenol, 2,4-dimethyl-6- tertiary butyl phenol, 2,4'-dimethyl-6-octyl .pounds, as sulfurized sperm oil, sulfurized jojoba oil, sulfurized resins or olefin polymers, paraffin wax polysulfides, sulfurized tall oil, sulfurized.

terpene hydrocarbons, methylene bis phenyl sulfides, etc.

Other corrosion inhibitors may also be present,

1 Approximate molecular weight 600.

When the anti-corrosive agents of the present.

. bases include metal as well as organic bases.

Metal bases include those of the alkali metals, Cu, Mg, Ca, Sr, Ba, Zn, Cd, Al, Sn, Pb, Cr, Mn, Fe, Ni, G0, etc. Organic bases include various nitrogen bases as primary, secondary, tertiary and quaternary amines.

Examples of detergent forming acids are the various fatty acids of say, 10 to carbon atoms, wool fat acids, parafiin wax acids (produced by oxidation of parafiin wax), chlorinated fatty acids, rosin acids, aromatic carboxylic acids in! cluding aromatic fatty acids, aromatic hydroxy fatty acids, paramn wax benzoic acids, various alkyl salicylic acids, phthalic acid mono ester, aromatic keto acids, aromatic ether acids; diphenols as di-(alkylphenol) sulfides and disulfides, methylene bis alkylphenols; sulfonic acids (zgmcentraon, per- Additive cent by Base 011 Result weight a Cno stearic acid- Mid Continent 400 vis. at 100 F. turbine raifinate Pertia)ct.'

o o. Alkyl succinic acid I 0. 022 do About 10% rusted in first 4 hours of test i (test then stopped). Alkyl succinic acid I 0.01

plus do Perfect. :1 Cyano stearic acid 0. 0075 Do 0. 015 California turbine rafllnate containing 0.25% by weight Do.

oi ditertiary butyl phenol (inhibitor). Do 0. 010 do About 15% rusted after 48 hours. 3 Cyano stearic acid"-.. 0.0075

p us Y Perfect. Alkyl succinic acid 1 0. 01

prising a predominant amount of a hydrocarbon fraction containing finely dispersed a corrosion retardant amount of an organic monobasic acid of between about 10 and about 60 carbon atoms and containing a radical selected from the group consisting of nitrile, nitro, and nitrosoradicals which is not more than four carbon moved from the acid radical.

2. The composition of claim 1 wherein said cor atoms rerosion retarding acid is an alpha cyano carboxylic acid containing a minimum 013 12 carbon atoms. 3. The composition of claim 1 wherein said vehicle is normally liquid.

4. A lubricating composition comprising a predominant amount of a refined mineral oil and a beneficiating amount of an oil-miscible compound having between about 10 and about 60 carbon such as may be produced by treatment of alkyl aromatic hydrocarbons or high boiling petroleum the calcium and barium salts of diphenol mono and poly sulfides. Non-metallic detergents include compounds such as the phosphatides (e. g., lecithin), certain fatty oils as rapeseed oil, voltolized fatty or mineral oils, etc.

Anti-oxidants comprise several types, for example. alkyl phenols such as 2,4,6-trimethyl atoms of the formula comprising hydrogen atoms, hydrocarbon and substituted hydrocarbon radicals, R is an organic radical, X is a radical containing an acidic hydrogen atom, Y represents a radical selected from the group consisting of a nitrile, nitro and nitroso radical and n represents a number selected from the group consisting of 0, 1, 2, and 3.

5. The composition of claim 4 in which said compound is an alpha cyano carboxylic acid.

6. The composition of claim 4 in which said mineral oil is a turbine oil.

7. The composition of claim 4 in which said com-pound has a, minimum of 12 carbon atoms and is present in the amount of about 0.001% to about 0.1%.

8. The composition of claim 4 which also contains a small amount or a corrosion inhibiting iii dicarboxylic acid containing aminimum of 16 carbon atoms.

9. An improved turbine oil comprising a refined mineral lubricating oil in which has been incorporated about (MIDI-0.1% of an oil miscible alpha cyano carboxylic acid having between about 10 and about 60 carbon atoms and about 0.001- 0.i% of an oil soluble alkyl succinic acid possessing a minimum of 16 carbon atoms.

10. A corrosion-preventive composition comprising a predominant amount of a substantially neutral vehicle containing finely dispersed there= in a corrosion retarding amount of an organic monobasic acid having between about 10 and about 60 carbons atoms and containing a radical selected from the group consisting of nitrile, nitro and nitroso radicals which is not more than 4 12 carbon atoms removed frdm the acid radical, and a small amount of a dicarboxylic acid containing at least 16 carbon atoms.

11. A corrosion-preventive composition comprising a predominant amount of a hydrocarbon fraction containing finely dispersed therein a corrosion retarding amount of an organic monobasic acid having between about 10 and about 60 carbon atoms and containing a radical selected from the group consisting of nitrile, nitroso and nitro radicals which is not more than 4 carbon atoms removed from the acid radical, and from about 0.001% to about 0.1% of an alkyl succinic acid having a minimum of about 16 carbon atoms.

WHJLIS G. ROUTSON. 

